Even with high endurance early game your character is pretty squishy. For example a grenade does 151 damage, your character armor is around 50, your endurance stat is around 6-7 and you base health is 150. The grenade can still kill you in one hit even with all those layers of protection. So what's the point of bumping the skill up if i can't see an actual gameplay ramification ?

I don't think endurance affects damage resistance, and I'm not sure that your regular armor numbers (ballistic/energy/radiation) reduce explosion damage.

Wow if basic ballistic doesn't even block that particular damage type thats bull. Did the armor rating in Fallout 3 block all incoming damage even explosion damage ? I don't remember.

Endurance rise your health points (difference might not be large at low levels) and makes you sprint longer. It does not reduce damage. To reduce explosive damage, you can add padding to some armours.